1. Field of the Invention
The present invention relates to a vehicle driving assist system that activates collision avoiding means, such as an alarm device and a vehicle speed limiting device, when a distance between the vehicle and a three-dimensional (3-D) obstacle ahead of the vehicle reaches a required activation distance.
2. Description of the Related Art
A variety of vehicle driving assist systems have been proposed in which 3-D obstacles such as preceding vehicles, oncoming vehicles, and pedestrians, that could possibly collide with one's own vehicle are detected by a laser radar or the like mounted on one's own vehicle, a physical distance between the 3-D obstacle and one's own vehicle is detected, and a warning is provided to a driver by an alarm if the distance is short.
On the other hand, a driver's perception ability to recognize the presence of a 3-D obstacle such as another vehicle and a pedestrian decreases in accordance with the degree of fatigue of the driver. To solve this problem, for example, Japanese Unexamined Patent Application Publication No. 6-243398 discloses a technology in which the degree of fatigue of the driver is detected and, if the degree of fatigue is high, the delay in recognizing a 3-D obstacle is prevented in advance by increasing the output power of a sensor that detects the presence of an object around a vehicle and a distance from the vehicle and by increasing the detection area.
However, it is known that the perception ability of the driver is decreased not only by the degree of fatigue of the driver but also by the complexity of the visual environment. For example, when 3-D objects such as electric poles and architectural structures are in the field of view in the region of a 3-D obstacle or when 3-D objects having a similar shape or size to the 3-D obstacle exist in the background of the 3-D obstacle, the 3-D obstacle blends in with the 3-D objects or is hidden by the 3-D objects. Therefore, the perception ability is decreased. However, almost all drivers are unaware of the decrease in their perception ability of a 3-D obstacle caused by a complex visual environment.
To solve this problem, one possibility is to increase in advance the sensitivity in detecting an obstacle by, for example, a laser radar. However, this solution sometimes provides over-assistance. Also, it disadvantageously decreases the accuracy of detection, and therefore, this solution decreases the usability and is not so practical.